The overarching goal of my research program is to understand how naturally occurring genetic variation results in evolved differences in behaviors. To examine these relationships, it is imperative to have a model organism that is both genetically and behaviorally variable, as well as genetically accessible. Natural populations have evolved an extraordinary diversity of behaviors. Developing and applying functional genetic tools and genomic resources to organisms from these natural populations provides an opportunity to uncover the mechanisms by which natural selection has produced these behavioral differences. Further, these approaches may provide general insights into the molecular and genetic bases of social behaviors in other species, such as humans. The blind Mexican cavefish has evolved a variety of morphological, physiological and behavioral traits, including reductions in social behaviors like aggression, relative to surface fish of the same species. My laboratory has focused on establishing methods to identify and functionally validate the role of naturally occurring genetic variants in cavefish behavioral evolution. The research program outlined here will leverage this evolutionary system to identify the genetic architecture underlying within-population differences in aggression, and to test the mechanisms by which differences in aggression evolve. Utilizing genetic mapping approaches, we will identify and functionally test candidate genes for aggressive behavior. Further, using integrative approaches, we determine the mechanisms by which naturally occurring genetic variants impact behavior. Together, this research program will provide important insights into the genetic and neural mechanisms underlying variability in complex behaviors.